PITTSBURGH, Pa. -- A senator seeking to model his career on that of some earlier Senate titan might choose one of the 19th century's ``great triumvirate'' -- Daniel Webster, Henry Clay, John Calhoun. Twentieth-century luminaries would include Mr. Republican, Robert Taft, or the pride of New York, Daniel Patrick Moynihan. But Alfonse D'Amato?

As New York's other senator from 1981 to 1999, D'Amato was the un-Moynihan, reveling in the title of Senator Pothole, a tribute, of sorts, to his unapologetic parochialism. So what is Rick Santorum, the third-ranking member of the Republican's Senate leadership and one of the nation's most prominent social conservatives, doing telling The New York Times that he wants to be like D'Amato, eschewing ``frilly stuff'' and practicing ``meat and potatoes'' politics?

He says, laughing, that he is trying to reassure constituents that he has not gone ``national'' by adopting un-Pennsylvania preoccupations. His campaign brochure ``50 Things You May Not Know About Rick Santorum,'' which includes such nuggets as: Santorum has been ``working closely with Bono'' to eliminate AIDS and world poverty, and legislating to regulate ``price gouging and unfair pricing by the big oil companies,'' and increasing the minimum wage, cracking down on ``puppy mills,'' battling Lyme disease -- and he sued Don Rumsfeld to stop the closure of a military facility in Pennsylvania.

Santorum, who is only 48 and looks 38 and has the ebullience of an 18-year- old, is seeking a third term. In 1994, he defeated the incumbent, Harris Wofford, the apple of many liberals' eyes, 49-47. In 2000, he was re-elected with 52 percent. His seat is one of the six most vulnerable Republican seats that Democrats must win to gain control of the Senate, and right now he is behind his opponent, Bob Casey Jr., the son of a popular former governor. Judging from recent polls, Santorum's deficit is between six to 18 points. Split the difference and he is 12 behind.

Twelve years ago, when he was a two-term congressman seeking a Senate seat and this columnist asked him how he would win, his pithy answer was: ``Guns.'' Pennsylvania's swarms of deer-slayers, who in hunting season must make the state sound like the third afternoon at Gettysburg, were feeling put-upon by President Clinton's crime bill. But Casey, too, supports gun owners' rights -- and, like Santorum, opposes abortion.

Casey, who so far has agreed to only one debate, and that one to occur before Labor Day, is trying to make this election a referendum on the incumbent. On two incumbents, actually, the other being President Bush, whose job approval among Pennsylvanians, in a poll taken immediately after the killing of Zarqawi, was 34 percent. Casey's mantra is that Santorum has voted ``98 percent of the time'' with the president. One of Santorum's counterpunches is that Casey agrees with the president in supporting the Senate's stance on immigration, whereas Santorum supports the House's ``enforcement'' first approach.

In recent presidential elections, Pennsylvania has been a steadily lighter shade of blue. In 1996, President Clinton carried it by 9.2 points. In 2000, Gore won by 4.2. In 2004, Kerry won by just 2.5.

About 40 percent of Pennsylvania's votes are cast in the southeast -- greater Philadelphia. If Kerry had received there the number of votes Gore got in 2000, instead of 280,000 more, Bush would have carried the state easily. Gov. Ed Rendell, Philadelphia's former two-term mayor, is on the ballot this year seeking a second term. He was regularly on that region's television newscasts for eight years. The suburbs contain a lot of voters who liked what they saw -- by cleaning the city's center, a Santorum aide says, Rendell ``ran the city for the suburbs'' -- and they relish voting for him, which will swell the turnout, to Casey's advantage. In the 2002 gubernatorial primary, running against Casey, Rendell received an astonishing 88 percent of the vote in populous Montgomery County. Santorum's social conservatism is a difficult sell there. Within Philadelphia, what are delicately called voting ``irregularities'' will probably be, the Santorum aide says laconically, ``less than usual,'' thanks to a bill the Legislature passed after Rendell vetoed a better bill.

Santorum receives rocky treatment from much of the state's media. He says that one journalist called the campaign with a single question -- ``Has Santorum ever met with a lobbyist?'' -- and that in 2000 the Philadelphia Daily News endorsed his opponent three times.

Still, Santorum is what Casey is not -- an enthusiastic, powerful campaigner. This race will tighten and around 11 p.m. November 7, might decide who controls the Senate in January 2007.